Bellows Pump

ABSTRACT

A bellows pump including in its pump case ( 5 ) a pair of plastic bellows ( 6 ) that expand and contract to alternatingly execute an output stroke that sends fluid out of pump chambers ( 7 ) defined by the bellows and a suction stroke that supplies fluid to the pump chambers. Metal actuation plates ( 10 ) are provided in the pump case so as to be movable in the axial direction, and these actuation plates are fixedly connected to the bottom walls ( 6   a ) of the bellows in peripheral portions thereof so that the opposed end faces ( 10   c,    6   g ) of the actuation plates and fluid-contact portions ( 6   f ), which are at the center of the bottom walls of the bellows and come into contact with fluid in the pump chambers, are set in a close contact to each other. The close-contact portions are sealed by O-rings ( 15 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bellows pump used for feeding andcirculating chemicals (e.g., chemicals and the like employed infabrication processes of semiconductors, liquid crystals, and organic EL(electroluminescence) elements) and slurries containing solid componentsand other slurry components (e.g., polishing fluid used in CMP (chemicalmechanical polishing) machines (semiconductor wafer surface-polishingmachines, in which CMP methods are used)).

2. Description of the Related Art

Of the bellows pumps of the type described above, one that is well-knownincludes a plastic, bottom-closed cylindrical bellows with its apertureportions connected to a pump case so as to be caused to expand andcontract in the axial direction. With the repeated extension andcontract, this bellows pump is adapted to alternate between an outputstroke, during which fluid is sent from a pump chamber formed by thesurrounding bellows to an output passage through an output check valve,and a suction stroke, during which the fluid is supplied from a suctionpassage to the pump chamber through a suction check valve (see, e.g.,FIG. 1 of Japanese Patent Application Laid-Open (Kokai) No. 2002-174180or FIG. 2 of Japanese Patent Application Laid-Open (Kokai) No.2012-122380)

In such a bellows pump, during the output stroke, the pump chamber iscompressed, and/or during the suction stroke, the pump chamber isdecompressed (negatively pressurized), which creates a risk that thebottom wall of the plastic bellow could be subject to deformation, suchas buckling and the like. For example, during the output stroke, inwhich the bellows is actuated to contract, there is a risk that thebottom wall of the bellows may be pushed out and buckle in a convexshape under the pressure of the pump chamber. On the other hand,conversely, during the suction stroke, in which the bellow is actuatedto expand, the pump chamber is negatively pressurized, thereby creatinga risk that the bottom wall of the bellows may be sucked in and bucklein a concave shape. Alternatively, when an air-cylinder mechanism (seeparagraph 0024 below) is used as a means for actuating the bellows toexpand and contract, there is a risk that the bottom walls of theplastic bellows could be subject to deformation such as buckling and thelike under the action of the pressurized air supplied to theintake/discharge spaces. For example, on the output stroke, during whichthe bellows is actuated to contract, the pressure in theintake/discharge space becomes lower than the pressure in the pumpchamber, thereby creating a risk that the bottom wall of the bellows maybe pushed in by the pressurized air supplied to the intake/dischargespace and may buckle in a concave shape into the pump chamber. Thus,when the bottom walls of the bellows undergoes deformation in thismanner, the bellows pump is unable to achieve the proper pumpfunctionality because of the unstable bellows-pump flow rates(output-fluid volumes) and circulating-fluid volumes, generation ofrandom fluctuations, and the like.

In such a bellows pump, the pump chamber is compressed on the outputstroke and/or on the suction stroke the pump chamber is decompressed(negatively pressurized), creating a risk that the bottom walls of theplastic bellows could be subject to deformation, such as buckling andthe like. For example, during the output stroke, in which the bellows isactuated to contract, there is a risk that the bottom wall of thebellows may be pushed out and buckle in a convex shape under thepressure of the pump chamber, and, conversely, during the suctionstroke, in which the bellows is actuated to expand, the pump chamber isnegatively pressurized, thereby creating a risk that the bottom wall ofthe bellows may be sucked in and buckle in a concave shape. Thus, whenthe bottom walls of the bellows undergoes deformation in this manner,the bellows pump cannot achieve proper pump functionality because ofsubstantial changes in pump-chamber volume, unstable bellows-pump flowrates (output-fluid volumes) and circulating-fluid volumes, generationof random fluctuations, and the like.

As disclosed in FIG. 1 of Japanese Patent Application Laid-Open (Kokai)No. 2002-174180 and in FIG. 2 of Japanese Patent Application Laid-Open(Kokai) No. 2012-122380, in bellows pumps, actuation plates provided soas to be movable in the axial direction are attached to the bottom wallsof the bellows, so that these actuation plates can work as a means forguiding the axial-direction motion (contractile actuation) of thebellows or as a means for synchronizing the contractile actuations ofthe two bellows in a double-acting bellows pump. Accordingly, usingactuation plates that are made of metal can allow the bottom walls ofthe bellows, which can be easily deformed because they are made ofplastic, to be reinforced.

However, as seen from FIG. 1 of Japanese Patent Application Laid-Open(Kokai) No. 2002-174180 and in FIG. 2 of Japanese Patent ApplicationLaid-Open (Kokai) No. 2012-122380, the bottom walls of the bellows areattached to the actuation plates only in the peripheral portionsthereof, which is why the above-described deformation induced by thepump-chamber pressure fluctuations during the output stroke and/orsuction stroke cannot be prevented in the central portion of the bottomwall of the bellows, that is, in the portion not attached to theactuation plate. For example, when the pump chamber is negativelypressurized during the suction stroke, there is a risk that the centralportion of the bottom wall of the bellows, which is not secured to anactuation plate, is subject to buckling deformation (and can be deformedin a concave shape) into the pump chamber by the action of the suctionforce produced by the negative pressure.

BRIEF SUMMARY OF THE INVENTION

Accordingly, in the light of the above-described circumstances, theobject of the present invention is to provide a bellows pump that iscapable of reliably preventing deformation, such as buckling, of thebottom wall of a bellows due to pressure fluctuations in the pumpchamber during the output stroke and/or suction stroke and that canachieve proper pump functionality, providing stable flow rates(output-fluid volumes) and circulating-fluid volumes and eliminatingrandom fluctuations.

In order to accomplish the above-described object, the present inventionprovides, in particular, the configuration (1) or the configuration (2)below for a bellows pump that is adapted, by causing plasticbottom-closed cylindrical bellows with its aperture portions connectedto the pump case to expand and contract in the axial direction, toalternate between the output stroke that sends fluid from a pumpchamber, defined by the surrounding bellows, to an output passagethrough an output check valve and the suction stroke that supplies fluidsupplied from a suction passage to the pump chamber through a suctioncheck valve.

(1) A metal actuation plate supported by the pump case so as to bemovable in the axial direction and the bottom wall of the bellows arefixedly connected in their peripheral portions, and opposed end faces ofthe actuation plate and the central area of the bottom wall of thebellows, that is, a fluid-contact portion that comes into contact withthe fluid in the pump chamber, are provided in a close contact with eachother, with such a close-contact portion being sealed by an annularsealing member.

(2) A metal actuation plate supported by the pump case so as to bemovable in the axial direction and the bottom wall of the bellows arefixedly connected in their peripheral portions, and a sealed space isformed by an annular sealing member provided between the opposed endfaces of the actuation plate and the central area of the bottom wall ofthe bellows, that is, a fluid-contact portion that comes into contactwith the fluid in the pump chamber, with such a sealed space beingfilled with an incompressible fluid.

In a preferred embodiment of the bellows pump of the present invention,the annular sealing member is an O-ring, and this said O-ring is held inengagement with an O-ring groove formed in the actuation plate or in thebottom wall of the bellows.

In the bellows pump of the present invention configured as described in(1) above, the fluid-contact portion, that is, the central area of thebottom wall of the bellows, is in a close contact with the actuationplate in a sealed state, and as a result, the fluid-contact portion andthe actuation plate are always held in a state of inseparable closecontact regardless of any pressure fluctuations occurring in the pumpchamber. In addition, in the bellows pump of the present inventionconfigured as described in (2) above, the sealed space formed betweenthe actuation plate and the fluid-contact portion, that is, the centralarea of the bottom wall of the bellows, is filled with incompressiblefluid, and as a result, the sealed space filled with such incompressiblefluid functions as a type of rigid body, and as a result, regardless ofany pressure fluctuations in the pump chamber, the fluid-contactportion, as well as the sealed space acting as a rigid body and theactuation plate, are held in such a state that they are in a mutuallyinseparable close contact.

As seen from the above, in either one of configurations (1) and (2), thefluid-contact portion of the bottom wall of the bellows is reinforced bythe metal actuation plate against the pressure of the pump chamber, anddeformation of the fluid-contact portion of the bottom wall of thebellows caused by the pressure fluctuations in the pump chamber can bereliably prevented. Alternatively, when the means used in the bellowspump of the present invention for actuating the bellows to expand andcontract is an air-cylinder mechanism (see paragraph 0024 below), thepressurized air supplied to the intake/discharge space for actuating thebellows to expand and contract is prevented from getting between thebottom wall of the plastic bellows and the metal actuation plate,thereby reliably preventing deformation of the bottom wall of theplastic bellows that is caused by the pressurized air supplied to theintake/discharge space. For this reason, the volume of the pump chamberduring the suction stroke and during the output stroke does not vary dueto the deformation of the bottom wall of the bellows while the flow rate(output-fluid volume) and circulating-fluid volume produced by the pumpremains stable, and the pump can achieve proper pump functionality. Inaddition, the bottom wall of the bellows itself does not have to possessa strength sufficient to prevent deformations induced by pump-chamberpressure fluctuations; accordingly, in the case of configuration (2), aswell as in the case of configuration (1), the bottom wall of the bellowscan be made as thin as possible, and this can ensure that the weight ofthe bellows is significantly reduced.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a cross-sectional side view illustrating one example of thebellows pump according to the present invention.

FIG. 2 is a cross-sectional front view of the main portion taken alongthe line II-II in FIG. 1.

FIG. 3 is a cross-sectional side view illustrating a modification of thebellows pump according to the present invention.

FIG. 4 is an enlarged view of the main portion of FIG. 3.

FIG. 5 is a cross-sectional front view taken along the line V-V in FIG.3.

FIG. 6 is a cross-sectional side view illustrating another modificationof the bellows pump according to the present invention.

FIG. 7 is an enlarged view of the main portion of FIG. 6.

FIG. 8 is a cross-sectional front view taken along the line VIII-VIII inFIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

The modes for carrying out the present invention will be describedspecifically with reference to the drawings.

FIG. 1 is a cross-sectional side view showing an example of the bellowspump according to the present invention, and FIG. 2 is a cross-sectionalfront view of the main portion taken along the line II-II in FIG. 1. Itshould be noted that in the description below the phrase “left andright” is intended to mean “left and right in FIG. 1”.

The bellows pump shown in FIG. 1 (hereinafter referred to as “firstpump) is a horizontal double-acting bellows pump used for feeding andcirculating fluid (e.g., chemicals and the like employed in thefabrication processes of semiconductors, liquid crystals, organic ELelements, and the like). The bellows pump is comprised of a pump case 5comprised of a pump head 3, having an output passage 1 and a suctionpassage 2 formed therein, and a pair of left and right cylinder cases 4,4 provided on both sides thereof. The bellows pump further includes: apair of left and right bellows 6, 6 respectively disposed inside of eachone of the cylinder cases 4 so as to make expansion and contraction(thus being expandable and contractable) in the axial direction(horizontal direction) of the pump head 3; a pair of left and right pumpchambers 7, 7 defined by being surrounded by the respective bellows 6; apair of left and right output check valves 8, 8 mounted to the pump head3 in a protruding fashion into each one of the pump chambers 7; and apair of left and right suction check valves 9, 9 provided in the pumphead 3 so as to protrude into each one of the pump chambers 7. Thisbellows pump is adapted, by alternatingly actuating the two or a pair ofbellows 6, 6 to expand and contract, to simultaneously carry out anoutput stroke that sends fluid out of one of the pump chambers 7 to theoutput passage 1 through the output check valve 8, and a suction strokethat supplies fluid from the suction passage 2 into the other pumpchamber 7 through the suction check valve 9. It should be noted that,with the exception of their left- and right-hand symmetrical structure,the two cylinder cases 4, 4, two bellows 6, 6, two pump chambers 7, 7,two output check valves 8, 8, and two suction check valves 9, 9 makingup the bellows pump have identical structures to each other.

The pump head 3 is shaped like a disk that has therein an output passage1 connected to a fluid-feed line and a suction passage 2 connected to afluid-supply line, and, as shown in FIG. 1, an upstream end of theoutput passage 1 and a downstream end of the suction passage 2 are openon the left and right sides thereof.

As seen from FIG. 1 to FIG. 4, each cylinder case 4 is a bottom-closedcylindrical casing mounted to the pump head 3. The pump case 5 is thusmade of the pump head 3 and the two cylinder cases 4, 4; and the spaceinside the pump case 5 is split into two in a side-to-side directionwith the pump head 3 in between.

As shown in FIG. 1 and FIG. 2, each bellows 6 is a bottom-closedcylinder made of plastic, and its peripheral wall 6 a has a bellowsconfiguration with a zigzag cross-section. By being expanded andcontracted in the axial direction (side-to-side horizontal direction),it enlarges and reduces the volume of the pump chamber 7. The open-endportion 6 b of each one of the bellows 6 is intimately secured orconnected to the pump head 3, with the space inside the bellows 6defining the pump chamber 7 closed by the pump head 3. Though it dependson the consistency and other characteristics of the fluid handled by thepump, fluororesins (such as polytetrafluoroethylene (PTFE) andperfluoroalkoxy (PFA) fluororesins and the like are preferably used asthe materials to make the bellows 6. In the shown example, PTFE isemployed. The bottom wall 6 c of each one of the bellows 6 is adisk-like part that has a constant thickness (thickness in the axialdirection) and an outer diameter that matches that of the peripheralwall 6 a (the maximum diameter thereof), and the end portion 6 d of atrough part of the peripheral wall 6 a is coupled to the bottom wall 6c.

As shown in FIG. 1, a disk-shaped actuation plate 10 made of metal (suchas stainless steel) is fixedly attached to the bottom wall 6 c of eachbellows 6. Each actuation plate 10 is comprised of a thin-walleddisk-shaped main portion 10 a and a thick-walled annular couplingportion 10 b formed in the peripheral portion thereof, and thisactuation plate 10 is fixedly attached to the bottom wall 6 c of thebellows 6 in such a manner that the main portion 10 a of the actuationplate 10 is abutted in a close contact to the bottom wall 6 c of thebellows 6 and the bottom wall 6 c is fitted into the annular couplingportion 10 b. In other words, the thickness of the bottom wall 6 c ofthe bellows 6 is set to be identical to or somewhat greater than thethickness (the thickness in the axial direction) (or depth) of theannular coupling portion 10 b of the actuation plate 10, and theperipheral portion 6 e (which is of the bottom wall 6 c and located moreoutboard of the portion used for coupling to the end portion 6 d of thetrough part of the peripheral wall 6 a) of the bottom wall 6 c of thebellows 6 is clamped between the main portion 10 a of the actuationplate 10 and a mounting plate 11 mounted to the coupling portion 10 b ofthe actuation plate 10. Accordingly, as shown in FIG. 1, the bottom wall6 c of the bellows 6 and actuation plate 10 are connected and integratedin the peripheral portion thereof such that the bottom wall 6 c of thebellows is in a close contact with the main portion 10 a of theactuation plate 10.

By way of connecting the actuation plates 10, 10 and the bellows 6, 6together with a plurality of (e.g., four) coupling rods 12, the twobellows 6, 6 are actuated in synchronism to expand and contract inopposite directions. In another words, as illustrated in FIG. 1, the twobellows 6, 6 are operatively connected to the actuation plates 10 suchthat when one of the bellows 6 is in its most contracted state, theother bellows 6 is in its most expanded state, and when one of thebellows 6 is actuated to contract, the other bellows 6 is actuated toexpand in unison therewith.

The plurality of coupling rods 12 connect the coupling portions 10 b, 10b, that are the peripheral portions of the actuation plates 10, 10, atlocations spaced apart at regular intervals in the circumferentialdirection; and by way of thus coupling the two actuation plates 10, 10with these coupling rods 12, the attachment of the bottom wall 6 c ofeach bellows 6 to each actuation plate 10 is obtained. Morespecifically, the coupling rods 12, which are provided inside thecylinder cases 4, 4, are held in the pump case 5 so as to be movable inthe axial direction by means of O-rings 13; and with nut members 14threadably mounted to and engaged with the distal threaded portions 12 athat pass through the coupling portions 10 b of the actuation plates 10and the mounting plates 11, the two actuation plates 10, 10 are coupledtogether while fixedly connecting the bottom wall 6 c of each bellows 6to each of the actuation plates 10. The thickness of the main portion 10a of the actuation plate 10 is set to have a strength sufficient toprevent the deformation under the action of the pressure in the pumpchamber 7, at least during the suction stroke and output stroke; and itis preferable that the main portion 10 a of the actuation plate 10 be asthin as possible as long as such strength to prevent deformation can beensured.

The means used for actuating the bellows 6 to expand and contractinclude, generally, piston-cylinder mechanisms, crank mechanisms,air-cylinder mechanisms, and the like; and in the shown embodiment, anair-cylinder mechanism is employed. More specifically, the actuatingmeans is adapted to actuate the bellows 6 to expand and contract in theaxial direction by supplying and discharging pressurized air 4 c throughintake/discharge ports 4 a formed in the bottom walls of the cylindercases 4 to/from intake/discharge spaces 4 b formed between the cylindercases 4 and the actuation plates 10 and bellows 6. The intake anddischarge of air through the two intake/discharge ports 4 a, 4 a iscarried out synchronously in an alternating manner, such that whenpressurized air 4 c is supplied to the intake/discharge space 4 bthrough one of the intake/discharge ports 4 a, air is simultaneouslydischarged from the other intake/discharge port 4 a, and as a result ofwhich the contractile actuation of the two bellows 6, 6, that is, thecontractile actuation of the two pump chambers 7, 7, is carried out insynchronism in opposite directions. In other words, a suction stroke (oran output stroke) in one of the pump chambers 7 is carried out insynchronism with an output stroke (or a suction stroke) in the otherpump chamber 7, and the switching between an output stroke (a stroke inwhich fluid is sent from the pump chamber 7 to the output passage 1through the output check valve 8) and a suction stroke (a stroke inwhich fluid is supplied from the suction passage 2 to the pump chamber 7through the suction check valve 9) in the two pump chambers 7, 7 iscarried out simultaneously. FIG. 1 illustrates the final state of thesuction stroke in the left-side pump chamber 7 and the output stroke inthe right-side pump chamber 7.

As shown in FIG. 1, each output check valve 8 is configured such that onthe suction stroke, during which the bellows 6 is actuated to expand(the volume of the pump chamber 7 changes so as to expand), the valveplug 8 b is held in the closed position under the urging force of thespring 8 a, while on the output stroke, during which the bellows 6 isactuated to contract (the volume of the pump chamber 7 changes so as tocontract), the valve plug 8 b is displaced to the open position againstthe urging force of the spring 8 a by the high pressure in the pumpchamber 7. Furthermore, as shown in FIG. 1, each suction check valve 9is configured such that on the output stroke, during which the bellows 6is actuated to contract, the valve plug 9 b is held in the closedposition by back pressure (the pressure of the pump chamber 7) and bythe urging force of the spring 9 a, while on the suction stroke, duringwhich the bellows 6 is actuated to expand, the valve plug 9 b isdisplaced to the open position against the urging force of the spring 9a as a result of a pressure drop in the pump chamber 7.

Of the components making the bellows pump above, those coming intocontact with fluid are formed by the materials suited to thecharacteristics of the fluid to be handled, etc. In the shown example,those components coming into contact with fluid are made offluororesin-base plastics, such as polytetrafluoroethylene, that havesuperior corrosion resistance and resistance to chemicals.

As seen from the above, in the first pump, the opposed end faces 10 c, 6g of the actuation plate 10 and the central area of the bottom wall 6 cof the bellows 6 are in a close contact with each other as shown inFIG. 1. In other words, the actuation plate 10 and the fluid-contactportion 6 f (the portion of the bottom wall 6 c located more inboard ofthe portion used for coupling to the end portion 6 d of the trough partof the peripheral wall 6 a) that comes into contact with the fluid inthe pump chamber 7 make a close contact relationship with each other. Inaddition, the close-contact portions 10 c, 6 g are sealed with anannular sealing member 15. In the shown example, the annular sealingmember 15 is an O-ring made of an incompressible elastic material (suchas fluororubber), and this O-ring 15 is held in engagement within anO-ring groove 15 a formed in the bottom wall 6 c of the bellows.

Accordingly, even if the pressure in the pump chamber 7 varies followingthe contractile actuation (contractile changes in pump-chamber volume)of the bellows 6, the bottom wall 6 c of the bellows is not deformed,and such problems as described in the section of the Related Art abovedo not arise, and proper pump functionality is achieved.

More specifically, in the pump chamber 7 (e.g., the left-side pumpchamber in FIG. 1) that is in a suction stroke, the suction stroke,during which the bellows 6 is actuated to expand, reduces the pressurein the pump chamber 7 and makes it negative, thereby creating the riskthat the central area, that is, the fluid-contact portion 6 f, of thebottom wall 6 c of the bellows having only its peripheral portion 6 econnected to the actuation plate 10 may be sucked into the negativelypressurized pump chamber 7 and buckle in a concave shape. However, thefluid-contact portion 6 f of the bottom wall 6 c of the bellows is in aclose contact with the main portion 10 a of the actuation plate 10 and,at the same time, the close-contact portions 6 g and 10 c are sealed bythe O-ring 15; accordingly, it does not separate from the main portion10 a of the actuation plate 10 under the action of the above-describedsuction force produced by the negative pressure. In other words, thefluid-contact portion 6 f of the bottom wall 6 c of the bellows is heldin a state of inseparable close contact with the main portion 10 a ofthe actuation plate 10. Therefore, the suction force that acts on thefluid-contact portion 6 f of the bottom wall 6 c of the bellows isreceived by the main portion 10 a of the metal actuation plate 10, andthus there is no risk that the fluid-contact portion 6 f deforms duringthe suction stroke.

On the other hand, in the other pump chamber 7 (e.g., the right sidepump chamber in FIG. 1) that is in an output stroke, the output stroke,during which the bellows 6 is actuated to contract, increases pressurein the pump chamber 7 and brings the chamber under high pressure,thereby creating the risk that the central area, that is, thefluid-contact portion 6 f, of the bottom wall 6 c of the bellows havingonly its peripheral portion 6 e connected to the actuation plate 10, maybe subject to buckling deformation in a convex shape under the action ofthe pushing force produced by the pressure in the pump chamber 7.However, the fluid-contact portion 6 f of the bottom wall 6 c of thebellows is in a close contact with the main portion 10 a of theactuation plate 10; accordingly, the above-described pushing forceacting on the fluid-contact portion 6 f is received by the main portion10 a of the metal actuation plate 10, and thus there is no risk that thefluid-contact portion 6 f deforms during the output stroke.

As seen from the above, in the first pump, the bottom walls 6 c of thebellows are prevented from being deformed by the pressure of the pumpchambers 7 during the suction stroke or the output stroke. As a result,problems such as unstable flow rates (output-fluid volumes) andcirculating-fluid volumes, and generation of random fluctuations due tosubstantial changes in pump-chamber volume do not arise, and proper pumpfunctionality is achieved.

Furthermore, in the first pump, the fluid-contact portion 6 f of thebottom wall 6 c of each of the bellows is reinforced by the actuationplate 10 as described above. Accordingly, the bottom walls 6 c of thebellows do not need to be so thick as to possess enough strength towithstand the pressure in the pump chambers 7, and the bottom walls 6 ccan be those that have a thickness that is necessary and sufficient forbeing connected to the actuation plates 10 via the mounting plates 11,distal threaded portions 12 a of the coupling rods 12, and nut members14. Accordingly, in comparison with the conventional bellows pumpdescribed in the section of the Related Art above, the bottom walls 6 cof the bellows can be made as thin as possible, and thus the weight ofthe bellows 6 can be reduced.

Incidentally, the configuration of the bellows pump according to thepresent invention is not limited to the one described above and can besuitably improved and modified without deviating from the principles ofthe present invention.

In the configuration of the first pump shown in FIG. 1, the twoactuation plates 10, 10 are coupled via the coupling rods 12 which aremovably supported by the pump case 5 in the axial direction, so thateach actuation plate 10 is supported by the pump case 5 via the couplingrods 12 so as to be movable in the axial direction; and further, by wayof coupling each actuation plate 10 to the coupling rods 12, theactuation plate 10 is connected to the bottom wall 6 c of the bellows 6with the mounting plate 11 in between. However, in the presentinvention, as a modification, the means used for supporting theactuation plates 10 in the pump case 5 and the means used for attachingthe actuation plates 10 to the bottom wall 6 c of the bellows can be, asshown in FIG. 3 to FIG. 5, separate and independent.

FIG. 3 is a cross-sectional side view illustrating a modification of thebellows pump of the present invention, and FIG. 4 is an enlarged view ofthe main portion of FIG. 3, and further FIG. 5 is a cross-sectionalfront view taken along the line V-V in FIG. 3. With the exception of thefollowing features, the bellows pump illustrated in FIG. 3 (hereinafterreferred to as “second pump”) is a horizontal double-acting bellows pumpof the same configuration as the first pump. For the components that areidentical to those of the first pump, the same reference numbers are inFIG. 3 to FIG. 5 as those in FIG. 1 and FIG. 2, and detaileddescriptions thereof are omitted.

As shown in FIG. 3 and FIG. 4, in the second pump, the bottom wall 6 cof each bellows 6 and the actuation plate 10 are shaped as disks of thesame diameter with a fixed thickness (thickness in the axial direction).The bottom wall 6 c of the bellows and the actuation plate 10 areconnected in a state of close contact by threadably engaging andfastening a plurality of connecting bolts 16 passing through theirperipheral portions 6 e, 10 e to a mounting plate 17. In the shownexample, as seen from FIG. 5, the peripheral portion 6 e of the bottomwall 6 c of the bellows 6 and the peripheral portion 10 e of theactuation plate 10 are connected by eight (8) connecting bolts 16arranged circumferentially at evenly spaced intervals. In addition, thethickness of the actuation plate 10 is set to possess a strengthsufficient to prevent deformation under the action of the pressure inthe pump chamber 7, at least during the suction stroke and outputstroke, and it is preferable that the actuation plate 10 be as thin aspossible as long as such strength to prevent deformation can be ensured.

An actuation shaft 20, which passes through and is supported by thebottom wall of the cylinder case 4 so as to be movable in the axialdirection through the medium of an O-ring 18 and a bearing ring 19, isintegrally formed in the central area of each one of the actuationplates 10. A disk-shaped coupling plate 21 is fixedly secured to the endof each actuation shaft 20 outside the cylinder case 4. The two couplingplates 21, 21 are disposed outside the cylinder cases 4, 4 and coupledtogether by an appropriate number of coupling rods 12, 12 (in the shownexample two (2)) that are provided in the pump case 5 so as to bemovable in the axial direction. Accordingly, because the two actuationplates 10, 10 are coupled together via the actuating shafts 20, 20, thecoupling plates 21, 21, and the coupling rods 12, 12, the two bellows 6,6 are actuated to in synchronism expand and contract in oppositedirections. In other words, as illustrated in FIG. 3, the two bellows 6,6 are operatively coupled such that when one of the bellows 6 is in itsmost contracted state, the other bellows 6 is in its most expandedstate, and when one of the bellows 6 is actuated to contract, the otherbellows 6 is actuated to expand in unison therewith.

In the same manner as in the first pump, the actuating means foractuating the bellows 6 to expand and contract is adapted to actuate thebellows 6 to expand and contract in the axial direction by supplying anddischarging pressurized air through intake/discharge ports (not shown)formed in the bottom walls of the cylinder cases 4 to/from theintake/discharge spaces 4 d formed between the cylinder cases 4,actuation plates 10, and the bellows 6. The intake and discharge of theair to/from the two intake/discharge spaces 4 d, 4 d is carried outsynchronously in an alternating manner, and, as a result, thecontractile actuation of the two bellows 6, 6, that is, the contractileactuation of the two pump chambers 7, 7, is carried out synchronously inopposite directions. In other words, a suction stroke (or an outputstroke) in one of the pump chambers 7 is carried out in synchronism withan output stroke (or a suction stroke) in the other pump chamber 7, andthe switching between the output stroke (a stroke in which fluid is sentfrom the pump chamber 7 to the output passage 1 through the output checkvalve 8) and the suction stroke (a stroke in which fluid is suppliedfrom the suction passage 2 to the pump chamber 7 through the suctioncheck valve 9) in the two pump chambers 7, 7 is carried outsimultaneously. FIG. 3 illustrates the final state of the suction strokein the left-side pump chamber 7 and the output stroke in the right-sidepump chamber 7.

As seen from the above, in this second pump, in the same manner as inthe first pump, as seen from FIG. 3 and FIG. 4, the opposed end faces 10c, 6 g of the actuation plate 10 and the central area of the bottom wall6 c of the bellows 6 are in a close contact with each other. In otherwords, the actuation plate 10 and the fluid-contact portion 6 f (theportion of the bottom wall 6 c located more inboard of the portion usedfor being connected to the end portion 6 d of the trough part of theperipheral wall 6 a) that comes into contact with the fluid in the pumpchamber 7 are in a closely contact relationship with each other. Inaddition, the close-contact portions 10 c, 6 g are sealed with theannular sealing member 15. In the shown example, in the same manner asin the first pump, the annular sealing member 15 is an O-ring made of anincompressible elastic material (such as fluororubber), and this O-ring15 is held in engagement within the O-ring groove 15 a formed in theactuation plate 10. The central portion of the fluid-contact portion 6 fof the bottom wall 6 c of each one of the bellows 6 is formed with around positioning protrusion 6 h that closely fits into a round recessedportion 10 d formed in the central portion of each one of the actuationplates 10, and thus the bottom walls 6 c of the bellows and theactuation plates 10 are abutted each other in a concentric manner.

Accordingly, in the second pump as well, in the same manner as in thefirst pump, even if the pressure in the pump chambers 7 varies followingthe contractile actuation (contractile changes in pump-chamber volume)of the bellows 6, the bottom walls 6 c of the bellows do not deformsince the bottom walls 6 c of the bellows are reinforced by the metalactuation plates 10, and such problems as described in the section ofthe Related Art above do not arise, and thus proper pump functionalityis achieved. In the second pump, since the coupling rods 12, 12 aredisposed outside the cylinder cases 4, 4, the volume of theintake/discharge spaces 4 d are smaller compared to the intake/dischargespaces 4 b in the first pump, and it is thus possible to reduce thevolume of the pressurized air used to actuate the bellows 6, 6 to expandand contract.

In addition, in the second pump, the fluid-contacts 6 f of the bottomwalls 6 c of the bellows are reinforced by the actuation plates 10.Accordingly, the bottom walls 6 c of the bellows do not need to be sothick as to possess enough strength to withstand the pressure in thepump chambers 7, and what is required for the bottom wall of the bellows6 is that it has a thickness that is necessary and sufficient to beattached to the actuation plates 10 by the connecting bolts 16 and themounting plates 17. In view of the above, in the same manner as in thefirst pump, the bottom walls 6 c of the bellows in the second pump canbe made as thin as possible in comparison with the conventional bellowspump described in the section of the Related Art above, and it ispossible to reduce the weight of the bellows 6.

In addition, although the first and second pump are adapted to bring theopposed end faces 10 c, 6 g of the actuation plates 10 and thefluid-contact portions 6 f of the bottom walls 6 c of the bellows 6 intoa close contact with each other while sealing these close-contact faces10 c, 6 g with the annular sealing members (the O-ring) 15, sealedspaces 22 as shown in FIG. 6 to FIG. 8 that are sealed by the annularsealing members 15 can be formed between the opposed end faces 6 g, 10c, so that the sealed spaces 22 are filled with an incompressible fluid23.

More specifically, FIG. 6 is a cross-sectional side view of anothermodification of the bellows pump according to the present invention,FIG. 7 is an enlarged view of the main portion of FIG. 6, and FIG. 8 isa cross-sectional front view taken along the line VIII-VIII in FIG. 6.With the exception of the following features, the bellows pumpillustrated in FIG. 6 (hereinafter referred to as “third pump”) is ahorizontal double-acting bellows pump of the same configuration as thesecond pump. The reference symbols identical to those of FIG. 3 and FIG.5 are assigned to the components identical to those of the second pumpin FIG. 6 to FIG. 8, and detailed descriptions thereof are omitted.

As seen from FIG. 6 and FIG. 7, in the third pump, a round recessedportion is formed in the outer surface of the fluid-contact portion 6 fof the bottom wall 6 c of each one of the bellows 6. In other words, thethickness (thickness in the axial direction) of the fluid-contactportion 6 f, that is, the central area of the bottom wall 6 c of thebellows, is made thinner than the thickness of the peripheral portion 6e of the bottom wall 6 c, and a space 22 corresponding to theabove-described round recessed portion is formed between the opposed endfaces 6 g, 10 c of the fluid-contact portion 6 f and the actuation plate10. This space 22 is made into a sealed space by way of using theannular sealing member 15 provided between the actuation plate 10 andthe peripheral portion 6 e of the bottom wall 6 c of the bellows 6. Inthe same manner as in the second pump, the annular sealing member 15 isan O-ring, and this O-ring 15 is held in engagement within the O-ringgroove 15 b formed in the actuation plate 10.

The sealed space 22 is completely filled with incompressible fluid 23(e.g., oil or another fluid).

Furthermore, as shown in FIG. 6 and FIG. 7, in this third pump, theactuating shafts 20 are the separate elements from the actuation plates10, and each actuation plate 10 and each actuation shaft 20 areintegrally coupled by threadably fastening the threaded portion 20 a ofthe distal end of the actuation shaft 20 to the internally threadedrecessed portion 10 f formed in the actuation plate 10 while sealing thethreaded connection portion with an O-ring 24.

With the above structure of the third pump, in the pump chamber 7 whichis under the suction stroke (e.g., the left-side pump chamberillustrated in FIG. 6), the bellows 6 is actuated to expand, thusreducing the pressure in the pump chamber 7 and making it negative,thereby creating a risk that the central area, that is, thefluid-contact portion 6 f, of the bottom wall 6 c of the bellows 6having only its peripheral portion 6 e attached to the actuation plate10 by two or more connecting bolts 16 may be sucked into the negativelypressurized pump chamber 7 and subject to buckling deformation in aconcave shape. However, the sealed space 22 formed between the opposedend faces 10 c, 6 g of the actuation plate 10 and the fluid-contactportion 6 f of the bottom wall 6 c of the bellows is completely filledwith the incompressible fluid 23, such as oil and the like; accordingly,the sealed space 22 filled with this incompressible fluid 23 canfunction as a type of rigid body. As a result, even when the pumpchamber 7 is negatively pressurized, the fluid-contact portion 6 f ofthe bottom wall 6 c of the bellows, the sealed space 22 that is filledwith the incompressible fluid 23 acting as a rigid body, and theactuation plate 10 are all held in a state of inseparable mutualcontact. Accordingly, the fluid-contact portion 6 f of the bottom wall 6c of the bellows 6 does not deform into a concave shape by being pulledinto the pump chamber 7, and thus the volume of the pump chamber 7 doesnot change on the suction stroke.

On the other hand, in another pump chamber 7 which is under the outputstroke (e.g., the right pump chamber illustrated in FIG. 6), the bellows6 is actuated to contract, thus increasing the pressure in the pumpchamber 7 and bringing the chamber under high pressure, thereby creatinga risk that the central area, that is, the fluid-contact portion 6 f, ofthe bottom wall 6 c of the bellows 6 with its peripheral portion 6 eonly connected to the actuation plate 10, may deform in a convex shapeinto the sealed space 22 under the action of the pushing force producedby the pressure in the pump chamber 7. However, the sealed space 22, asdescribed above, can function as a type of rigid body filled with theincompressible fluid 23, and the pushing force produced by the pressurein the pump chamber 7 that acts on the fluid-contact portion 6 f of thebottom wall 6 c of the bellows is received by the metal actuation plate10 through the medium of the sealed space 22 acting as a rigid body.Consequently, there is no risk that the fluid-contact portion 6 f maydeform during the output stroke, and the volume of the pump chamber 7does not change on the output stroke.

As seen from the above, as in the first and second pumps, the bottomwalls 6 c of the bellows of the third pump are not deformed by thepressure fluctuations in the pump chambers 7 during the suction strokeor the output stroke. Accordingly, problems such as unstable flow rates(output-fluid volumes) and circulating-fluid volumes, and generation ofrandom fluctuations due to substantial changes in pump-chamber volume donot arise, and proper pump functionality is achieved.

In addition, in the third pump, as described above, the fluid-contactportions 6 f of the bottom walls 6 c of the bellows are reinforced bythe actuation plates 10 through the medium of the sealed spaces 22.Accordingly, the bottom walls 6 c of the bellows may have a thicknessthat is necessary and sufficient for attaching its peripheral portions 6e to the actuation plates 10 by means of the connecting bolts 16 andmounting plates 17, and the thickness of the fluid-contact portions 6 f,that is, the central areas, can be reduced even more compared to thefirst and second pumps, and further the weight of the bellows 6 can bereduced significantly.

It should be noted that in addition to applications involvingdouble-acting bellows pumps such as the first through third pumps, thepresent invention is suitably applicable to single-acting bellows pumps.

1. A bellows pump adapted to cause a plastic bottom-closed cylindrical bellows with aperture portions thereof connected to a pump case to expand and contract in an axial direction thereof, thereby alternating between an output stroke in which fluid is sent from a pump chamber defined by the bellows to an output passage through an output check valve and a suction stroke in which fluid is supplied from a suction passage to the pump chamber through a suction check valve, wherein: metal actuation plates are provided in the pump case so as to be movable in an axial direction thereof, the actuation plates and bottom walls of the bellows are fixedly connected in peripheral portions thereof, opposed end faces of the actuation plates and the fluid-contact portions are set in a close contact with each other, the fluid-contact portions being central areas of the bottom walls of the bellows and coming into contact with fluid in the pump chamber, and said close-contact portions are sealed with annular sealing members.
 2. A bellows pump adapted to cause a plastic bottom-closed cylindrical bellows with aperture portions thereof connected to a pump case to expand and contract in an axial direction thereof, thereby alternating between an output stroke in which fluid is sent from a pump chamber defined by the bellows to an output passage through an output check valve and a suction stroke in which fluid is supplied from a suction passage to the pump chamber through a suction check valve, wherein: metal actuation plates are provided in the pump case so as to be movable in an axial direction thereof, the actuation plates and bottom walls of the bellows are fixedly connected in peripheral portions thereof, sealed spaces are provided between opposed end faces of the actuation plates and central areas of the bottom walls of the bellows, said spaces being sealed by annular sealing members, and said sealed spaces are filled with incompressible fluid.
 3. The bellows pump according to claim 1, wherein the annular sealing members O-rings, and said O-rings are held in engagement with O-ring grooves formed in either one of the bottom walls of the bellows and the actuation plates.
 4. The bellows pump according to claim 2, wherein the annular sealing members O-rings, and said O-rings are held in engagement with O-ring grooves formed in either one of the bottom walls of the bellows and the actuation plates. 